Recording tape cartridge and method of manufacturing said cartridge

ABSTRACT

In a recording tape cartridge, cut-out portions are formed at an inner peripheral edge portion of a metal plate. By providing gates at the cut-out portions, the metal plate is insert molded without depending on submarine gates. Because the gates are provided, at the time of molding a reel hub, a molding material flows radially from a hole portion toward a tubular portion and a lower flange.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional of application Ser. No. 10/610,712 filed Jul. 2,2003 now U.S. Pat. No. 6,913,218, which application claims priorityunder 35 USC 119 from Japanese Patent Application No. 2002-196706, thedisclosure of each of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a recording tape cartridge rotatablyaccommodating a single reel on which a recording tape is wound.

2. Description of the Related Art

Conventionally, among recording tape cartridges used as recording mediaused in external storage devices of computers for example, a type isknown in which a single reel is rotatably accommodated in the recordingtape cartridge. A recording tape, such as a magnetic tape, is wound onthe reel within the recording tape cartridge.

The magnetic tape is used for, for example, storage of data of acomputer, and there are cases in which important information is recordedthereon. In this case, the recording tape cartridge is structured suchthat the magnetic tape cannot be inadvertently pulled-out therefrom atthe time when the recording tape cartridge is not in use (e.g., when therecording tape cartridge is being stored), so that trouble such asjamming of the tape or the like does not occur.

The reel is structured by a reel hub and upper and lower flanges whichare provided at the both end portions of the reel hub. As shown in FIGS.8 and 9, a reel hub 100 and a lower flange 102 are molded integrally.After molding, an upper flange 104 is welded so that a reel 106 isformed.

The reel hub 100 has a driven gear 108 which meshes with a driving gear105 which transmits driving force from a driving device 103 of a drivedevice. An annular metal plate 110 for magnetic attraction is providedat the inner side of the driven gear 108. Due to the metal plate 110being attracted to a magnet (not shown) provided at the driving device103 of the drive device, axial offset is prevented, and the state inwhich the driven gear 108 and the driving gear 105 are meshed togetheris maintained.

Moreover, a lock gear 112 is formed at an inner surface of the reel hub100 which is positioned at the opposite side of the driven gear 108. Thelock gear 112 meshes with a braking gear 114A provided at a brakingmember 114, so as to prevent rotation of the reel 106.

A lock releasing portion 107 provided at the driving device 103 of thedrive device can be inserted through a hole 110A formed in the metalplate 110. The braking member 114 is pushed up by the lock releasingportion 107, the meshed state of the braking gear 114A and the lock gear112 is cancelled, and the reel 106 becomes able to rotate.

Three through holes 116 are formed at equal intervals in the metal plate110. As shown in FIG. 10A, a reduced diameter portion 116A is formed atthe inner peripheral edge portion of the through hole 116. A boss 118,which is of a size such that it can be inserted through the reduceddiameter portion 116A, stands erect at the reel hub 100 at the positionwhere the metal plate 110 is mounted.

After the reel hub 100 and the lower flange 102 (see FIG. 9) are molded,as shown in FIG. 10B, the bosses 118 are inserted through the reduceddiameter portions 116A. As shown in FIG. 10C, the distal end portions ofthe bosses 118 are caulked, such that the metal plate 110 is preventedfrom coming off of the reel hub 100.

In this way, the metal plate 110 and the reel hub 100 are made integral.However, after the reel hub 100 and the lower flange 102 are molded, themetal plate 110 is made integral with the reel hub 100 by outsertmolding. Thus, the number of work processes increases, which leads to anincrease in manufacturing costs.

Thus, it has been thought to make the metal plate 110 integral with thereel hub 100 by insert molding. However, in order to reduce thedispersion of the reel hub 100 caused by molding, it is better to setthe gate positions as near as possible to the axial center side.

The annular metal plate 110 is disposed at the axial center side of thereel hub 110. Thus, there is a method in which the molding material isfilled in from the inner surface side of the reel hub 100 so as to flowover the hole 110A of the metal plate 110 by submarine gates. In casesin which the hole 110A of the metal plate 110 is small, it is difficultto provide a plurality of submarine gates.

SUMMARY OF THE INVENTION

In view of the aforementioned, an object of the present invention is toprovide a recording tape cartridge having an inexpensive reel in whichthere is little dispersion due to molding.

The present invention provides a recording tape cartridge rotatablyaccommodating a single reel on which a recording tape is wound. The reelis structured by a hub, annular flanges, an annular metal plate, cut-outportions, and gates. The hub is hollow and on which the recording tapeis wound. The annular flanges are provided at both end portions of thehub and holding transverse direction end portions of the recording tapewound around the hub. The annular metal plate is insert molded to an endportion of the hub. The cut-out portions are formed at an innerperipheral edge portion of the metal plate. The gates for filling of amolding material are provided in the cut-out portions.

In the present invention, a plurality of cut-out portions are formed atan inner peripheral edge portion of a metal plate. By providing gates inthe cut-out portions, the metal plate can be insert molded withoutdepending on submarine gates. Thus, no problems arise even if the holeportion of the metal plate is small. Accordingly, there is no need tooutsert mold the metal plate. The number of work processes can bereduced, and the cost of the reel can be reduced.

Further, by providing the gates in the cut-out portions which are formedat the inner peripheral edge portion of the metal plate, when the reelhub is molded, the molding material flows radially from the innerperipheral edge side of the reel hub toward the outer peripheral edgeside. Thus, there is little fluctuation in the pressure of the moldingmaterial, and the residual stress can be decreased. Therefore,dispersion of the reel hub caused by molding can be reduced, and thedimensional accuracy can be increased.

Moreover, by forming the cut-out portions and providing the gates in thecut-out portions, the molding material is filled in the cut-outportions, and it is possible to prevent the metal plate from rotating.In addition, by forming the inner peripheral edge portion of the cut-outportion in a particular shape, the molding material flows in at theinner peripheral edge portion along that shape. Thus, it is possible toprevent the metal plate from being pulled off.

Further, an annular portion, which connects the plurality of gates alongthe inner peripheral edge portion of the metal plate, may be provided.In this way, the molding material which is filled in from the gatesflows at the reverse surface of the metal plate from the gates towardthe outer edge side of the reel hub, and also flows to the annularportion. Thus, the molding material flows radially from the entireperiphery of the inner peripheral edge portion of the reel hub towardthe outer peripheral edge portion side, and the weld line can be made tobe inconspicuous. Accordingly, the problem of cracking due to changesover time does not arise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a recording tape cartridgerelating to an embodiment of the present invention.

FIG. 2 is an exploded perspective view, as seen from below, of therecording tape cartridge relating to the embodiment.

FIG. 3 is a sectional view of the recording tape cartridge relating tothe embodiment, and a driving device of a drive.

FIG. 4 is a rear view of a reel provided at the recording tape cartridgerelating to the embodiment.

FIG. 5 is a schematic sectional view showing a state in which a metalplate is fixed in a mold for molding a reel hub and a lower flange ofthe reel provided at the recording tape cartridge relating to theembodiment.

FIG. 6 is a schematic sectional view showing a state in which anothermetal plate is fixed in the mold for molding the reel hub and the lowerflange of the reel provided at the recording tape cartridge relating tothe embodiment.

FIG. 7 is a schematic sectional view showing a state in which yetanother metal plate is fixed in the mold for molding the reel hub andthe lower flange of the reel provided at the recording tape cartridgerelating to the embodiment.

FIG. 8 is an exploded perspective view, as seen from below, of aconventional recording tape cartridge.

FIG. 9 is a sectional view of the conventional recording tape cartridge,and a driving device of a drive.

FIGS. 10A through 10C are sectional views showing a method of outsertmolding a metal plate at a reel hub.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a summary of a recording tape cartridge (hereinafter called“magnetic tape cartridge”) relating to an embodiment of the presentinvention will be given.

As shown in FIGS. 1 through 3, the recording tape cartridge 10 is formedby an upper case 20 and a lower case 30 which are formed of a syntheticresin in substantial box-shapes. A peripheral wall 22 of the upper case20 and a peripheral wall 32 of the lower case 30 are welded together by,for example, ultrasonic welding.

Tubular walls 24, 34 stand upright at the inner surfaces of the uppercase 20 and the lower case 30, respectively. The inner diameters of thetubular walls 24, 34 are formed to be slightly larger than the outerdiameters of an upper flange 52 and a lower flange 54 of a reel 50, andthe reel 50 is rotatably accommodated at the inner sides of the tubularwalls 24, 34.

A plurality of ribs 23 are provided between the tubular wall 24 and theperipheral wall 22. A plurality of ribs 33 are provided between thetubular wall 34 and the peripheral wall 32. The tubular wall 24 and theperipheral wall 22 are connected by the ribs 23, and the tubular wall 34and the peripheral wall 32 are connected by the ribs 33. The tubularwalls 24, 34 and the peripheral walls 22, 32 are thereby strengthened.

The reel 50 is structured by a tubular reel hub 56, and the upper flange52 and the lower flange 54 which are provided at the both end portionsof the reel hub 56. The widthwise direction end portions of a magnetictape 12, which serves as an information recording/playback medium andwhich is wound on the reel hub 56, are held at the upper flange 52 andthe lower flange 54.

A bottom wall 58 is provided at the lower flange 54 of the reel hub 56.A hole portion 58A is formed in the center of the bottom wall 58. Anannular reel gear 60 (driven gear) projects out from the bottom wall 58at the bottom surface side of the bottom wall 58.

The reel gear 60 can emerge from a circular open hole 38 provided at thecenter of the lower case 30, and meshes with a driving gear 63 providedat a driving device 65 of a drive device so as to transmit rotationalforce to the reel 50.

An annular metal plate 62 is molded integrally at the inner side of thereel gear 60. Due to the metal plate 62 being attracted to a magnet (notshown) provided at the driving device 65 of the drive device, axialoffset is prevented, and the meshed-together state of the reel gear 60and the driving gear 63 can be maintained.

An annular groove 64 is provided at the outer side of the reel gear 60.The reel 50 is positioned with respect to the lower case 30 due to a rib36, which stands erect at the peripheral edge portion of the open hole38 provided at the case 30, being inserted into the annular groove 64.

An annular reel gear 70 is formed at the top surface side of the bottomwall 58 of the reel hub 56. The reel gear 70 can mesh with a brakinggear 82 which is formed at the outer peripheral portion of the bottomsurface of a substantially disc-shaped braking member 80 which can beaccommodated within the reel hub 56.

Ribs 84, which are substantially U-shaped as seen in plan view (and arereferred to hereinafter as “U-shaped ribs”), stand erect at the topsurface of the braking member 80 such that the open sides thereof opposeeach other. A pair of anchor pins 66 are provided so as to hang downfrom the center of the inner surface of the upper case 20, and canengage with the U-shaped ribs 84.

In this way, the U-shaped ribs 84 of braking member 80 can move alongthe anchor pins 66 and within the reel hub 56, and rotation of thebraking member 80 is impeded. Thus, when the magnetic tape cartridge 10is not being used, the braking gear 82 of the braking member 80 and thereel gear 70 mesh together, and rotation of the reel 50 is prevented.

An annular groove 86 is provided at the outer side of the U-shaped ribs84 of the braking member 80. An annular projection 68 projects at theouter side of the anchor pins 66 of the upper case 20. A spring 16 isprovided between the braking member 80 and the upper case 20, and isheld by the annular projection 68 and the annular groove 86.

In this way, the braking member 80 is urged toward the reel gear 70, andthe braking gear 82 and the reel gear 70 can strongly mesh together.Thus, inadvertent rotation of the reel 50 is reliably prevented.

A projection 88, which is substantially solid-cylindrical and which canbe inserted through the hole portion 58A, projects at the center of thebottom surface of the braking member 80. Before the reel gear 60 mesheswith the driving gear 63 and rotational force is transmitted to the reel50, a meshing releasing pin 69, which is provided at the distal endportion of a rotating shaft 67 provided at the driving device 65 of thedrive device, abuts the projection 88. The braking member 80 is therebypushed upwardly against the urging force of the spring 16, and themeshing of the braking gear 82 and the reel gear 60 is released. In thisway, the reel 50 is able to rotate.

Opening portions 18, 19 are formed at the front left corner portions ofthe peripheral wall 22 of the upper case 20 shown in FIG. 1 and theperipheral wall 32 of the lowercase 30, respectively. The openingportions 18, 19 are for enabling the magnetic tape 12, which is wound onthe reel 50, to be pulled out to the exterior.

A leader block 40 is attached to the distal end portion of the magnetictape 12. An unillustrated pull-out pin provided at the drive deviceengages with a concave portion 42 formed in the leader block 40, and themagnetic tape 12 is taken-up by a take-up reel provided at the drivedevice. At this time, the reel 50 and the take-up reel are driven torotate synchronously, and data is recorded or played-back while themagnetic tape 12 is successively taken-up onto the take-up reel.

When the magnetic tape cartridge 10 is not being used, the leader block40 is anchored at the peripheral edges of the opening portions 18, 19,and the opening portions 18, 19 are closed by the leader block 40.

Next, the reel of the recording tape cartridge relating to theembodiment of the present invention will be described.

As shown in FIG. 3, the reel hub 56 and the lower flange 54, whichstructure the reel 50, are molded integrally. After the reel hub 56 andthe lower flange 54 are molded, the upper flange 52 is welded to thereel hub 56 by ultrasonic waves, and the reel 50 is formed.

The metal plate 62 is provided at the inner side of the reel gear 60formed at the reel hub 56. The metal plate 62 is inserted into a mold 81(see FIG. 5) which molds the reel hub 56 and the lower flange 54, andthe metal plate 62 is molded integrally with the reel hub 56 and thelower flange 54.

As shown in FIG. 5, a fixed side mold plate 83 and a movable side moldplate 85 are provided at the mold 81. In the state in which the metalplate 62 is fixed at the fixed side mold plate 83, the mold 81 isclamped. A molding material is filled into a cavity 87 formed by thefixed side mold plate 83 and the movable side mold plate 85, and thereel hub 56 and the lower flange 54 (refer to FIG. 3 for both) aremolded.

Here, an annular concave portion 89, which has an inner diameter whichis substantially the same as the outer diameter of the metal plate 62,is formed in a recessed manner in the fixed side mold plate 83. In thestate in which the mold 81 is open, the metal plate 62 is set within theannular concave portion 89, so as to be positioned with respect to thefixed side mold plate 83.

Moreover, an annular magnetic body 72 is disposed at the bottom surfaceof the annular concave portion 89 at the fixed side mold plate 83. Themagnetic body 72 is fixed such that the metal plate 62 set within theannular concave portion 89 does not fall out. Note that the magneticbody 72 is not needed in a case in which the metal plate 62 is reliablyfixed within the annular concave portion 89 due to, for example, thedepth of the annular concave portion 89.

As shown in FIGS. 4 and 5, three cut-out portions 76 are provided atuniform intervals at an inner peripheral edge portion 74 of the metalplate 62. An enlarged diameter portion 76A is provided at the innerperipheral edge portion of the cut-out portion 76. When the metal plate62 is set within the annular concave portion 89 of the fixed side moldplate 83, the metal plate 62 is set such that the enlarged diameterportion 76A side thereof becomes the bottom surface side of the annularconcave portion 89.

A gate 90, which is for filling the molding material into the cavity 87by a pin gate, is provided within the cut-out portion 76. Moreover, agap 92 is provided between the inner peripheral edge portion 74 of themetal plate 62 and an inner peripheral wall 89A of the annular concaveportion 89. The molding material flows into the gap 92, such that anannular portion 93, which joins the gates 90 along the inner peripheraledge portion 74 of the metal plate 62, is provided.

Through holes 78 are formed between the adjacent cut-out portions 76, ona circle which is concentric with the inner peripheral edge portion 74of the metal plate 62. An enlarged diameter portion 78A is provided atthe inner peripheral edge portion of the through hole 78, in the sameway as and at the same surface side of the metal plate 62 as the innerperipheral edge portion of the cut-out portion 76.

Next, operation of the reel hub forming the reel of the recording tapecartridge relating to the embodiment of the present invention will bedescribed.

As shown in FIGS. 3 through 5, the plurality of cut-out portions 76 areformed in the inner peripheral edge portion 74 of the metal plate 62,and the gates 90 are provided in the cut-out portions 76. The metalplate 62 can thereby be insert molded without depending on submarinegates. Thus, there is no problem even if the hole portion 58A of thereel hub 56 is small. Accordingly, there is no need to outsert mold themetal plate 62, the number of work processes can be drastically reduced,and the cost of the reel 50 can be decreased.

Further, by providing the gates 90 in the cut-out portions 76 formed atthe inner peripheral portion 74 of the metal plate 62, when the reel hub56 is molded, the molding material flows radially toward a tubularportion 56A and the lower flange 54 from the hole portion 58A of thereel hub 56. Thus, there is little variation in pressure of the moldingmaterial, and the residual stress can be made to be small. Therefore,dispersion of the reel hub 56 due to molding can be decreased, and thedimensional accuracy can be improved.

Moreover, by forming the cut-out portions 76 in the inner peripheralportion 74 of the metal plate 62 and providing the gates 90 in thecut-out portions 76, the molding material is filled into the cut-outportions 76, and it is possible to prevent rotation of the metal plate62. The same effects are achieved with respect to the through holes 78as well.

Moreover, by making the inner peripheral edge portion of the cut-outportion 76 and the inner peripheral edge portion of the through hole 78have the above-described configurations, the molding material flows inthese inner peripheral edge portions along the configurations thereof.Thus, the metal plate 62 can be prevented from being pulled-out.

Moreover, the gap 92 is provided between the inner peripheral edgeportion 74 of the metal plate 62 and the inner peripheral wall 89A ofthe annular concave portion 89, and the molding material flows into thisgap 92. The molding material filled in from the gates 90 thereby flowsradially toward the tubular portion 56A and the lower flange 54 from theinner peripheral edge portion 74 of the metal plate 62, and it ispossible to make the well drain inconspicuous. Accordingly, the problemof cracks arising due to changes over time does not arise.

Here, by forming the inner peripheral edge portions of the cut-outportions 76 and the inner peripheral edge portions of the through holes78 to have the above-described configurations, the strength againstpulling the metal plate 62 out is increased. However, it is notabsolutely necessary to provide both the cut-out portions 76 and thethrough holes 78.

Thus, it is not absolutely necessary to form the through holes 78 in themetal plate 62. By not providing the through holes 78 in the metal plate62, the surface area of the metal plate 62 increases, and the attractiveforce with the magnet (not illustrated) provided at the driving device65 of the drive device can be improved.

The metal plate 62 is prevented from being pulled-out by forming thecut-out portions 76 and the through holes 78 in the above-describedconfigurations. However, the present invention is not limited to thesame. For example, as shown in FIG. 6, pulling-out of a metal plate 94can be prevented by providing a taper portion 94A at the outerperipheral edge portion of the metal plate 94 and by placing the metalplate 94 such that the reduced diameter side of this taper portion 94Abecomes the bottom surface side of an annular concave portion 95.Further, as shown in FIG. 7, a metal plate 96 can be prevented frombeing pulled-out by forming an outer peripheral edge portion 96A of themetal plate 96 in the above-described configuration.

In addition, as shown in FIG. 4, the gap 92 is provided between theinner peripheral edge portion of the metal plate 62 and the innerperipheral wall 89A of the annular concave portion 89, and the annularportion 93 connecting the gates 90 is provided. However, the annularportion 93 is not absolutely necessary, and a state in which the gates90 are separated suffices.

Here, as shown in FIG. 5, the annular concave portion 89 is formed in arecessed manner in the fixed side mold plate 83 in order to fix themetal plate 62 at the fixed side mold plate 83. However, the annularconcave portion 89 is not absolutely necessary.

For example, as shown in FIG. 7, in a case in which the annular portion93 (see FIG. 4) is not provided at an inner peripheral edge portion 96Bof the metal plate 96, the metal plate 96 may be fixed to a fixed sidemold plate 91 by forming a solid cylindrical projecting portion 91A atthe fixed side mold plate 91 and placing the inner peripheral edgeportion 96B of the metal plate 96 at the projecting portion 91A.

Because the present invention has the above-described structure, byforming a plurality of cut-out portions at the inner peripheral edgeportion of a metal plate and by providing gates within the cut-outportions, the metal plate can be insert molded without depending onsubmarine gates. Thus, no problem arises even if the hole portion of themetal plate is small. Accordingly, there is no need to outsert mold themetal plate, and the number of work processes can be reduced, and thecost of the reel can be decreased. Moreover, by providing the gates inthe cut-out portions formed at the inner peripheral edge portion of themetal plate, when the reel hub is molded, the molding material flowsradially from the inner peripheral edge side of the reel hub toward theouter peripheral edge side. Therefore, there is little variation in thepressure of the molding material, and the residual stress can be made tobe small. Thus, dispersion of the reel hub due to molding can bedecreased, and the dimensional accuracy can be improved.

1. A method of manufacturing a recording tape cartridge which rotatablyaccommodates a reel having a hub which is hollow and on which therecording tape is wound; annular flanges provided at both end portionsof the hub and holding transverse direction end portions of therecording tape wound around the hub; and an annular metal plate which isinsert molded to an end portion of the hub, said method comprising thesteps of: forming at least one cut-out portion at an inner peripheraledge portion of the metal plate; and providing, in the cut-out portion,a gate for filling of a molding material.
 2. The method of manufacturinga recording tape cartridge of claim 1, wherein the step of providing thegate includes providing a plurality of the gates, and further includesproviding, in the metal plate, an annular portion which connects theplurality of gates along the inner peripheral edge portion of the metalplate.
 3. The method of manufacturing a recording tape cartridge ofclaim 1, wherein the step of forming at least one cut-out portionincludes providing three cut-out portions at uniform intervals at theinner peripheral edge portion of the metal plate, and further includesproviding an enlarged diameter portion at an inner peripheral edgeportion of the cut-out portion.
 4. The method of manufacturing arecording tape cartridge of claim 1, further comprising a step ofproviding a taper portion at an outer peripheral edge portion of themetal plate.
 5. The method of manufacturing a recording tape cartridgeof claim 1, further comprising a step of providing a step at an outerperipheral edge portion of the metal plate.
 6. The method ofmanufacturing a recording tape cartridge of claim 1, further comprisinga step of using a mold which integrally molds the annular flanges andthe hub, wherein the mold has a fixed side mold plate and a movable sidemold plate, and said method further comprises a step of placing andfixing the inner peripheral edge portion of the metal plate at asolid-cylindrical projecting portion provided at the fixed side moldplate.
 7. The method of manufacturing a recording tape cartridge ofclaim 2, further comprising a step of using a mold which integrallymolds the annular flanges and the hub, wherein the mold has a fixed sidemold plate and a movable side mold plate, and an annular concave portionhaving an inner diameter which is the same as an outer diameter of themetal plate is formed in the fixed side mold plate, and providing of theannular concave portion includes providing a gap between the innerperipheral edge portion of the metal plate and an inner peripheral wallof the annular concave portion of the fixed side mold plate.
 8. Themethod of manufacturing a recording tape cartridge of claim 3, furthercomprising the step of forming through holes, on a circle concentricwith the inner peripheral edge portion of the metal plate, between thecut-out portions which are adjacent.
 9. The method of manufacturing arecording tape cartridge of claim 3, further comprising a step of usinga mold which integrally molds the annular flanges and the hub, whereinthe mold has a fixed side mold plate and a movable side mold plate, andan annular concave portion having an inner diameter which is the same asan outer diameter of the metal plate is formed in the fixed side moldplate, and said method further comprises a step of placing the metalplate in the annular concave portion and positioning the metal platewith respect to the fixed side mold plate.
 10. The method ofmanufacturing a recording tape cartridge of claim 4, further comprisinga step of using a mold which integrally molds the annular flanges andthe hub, wherein the mold has a fixed side mold plate and a movable sidemold plate, and an annular concave portion having an inner diameterwhich is the same as an outer diameter of the metal plate is formed inthe fixed side mold plate, and said method further comprises the step ofplacing a reduced diameter portion of the taper portion so as to face abottom surface of the annular concave portion.
 11. The method ofmanufacturing a recording tape cartridge of claim 9, wherein positioningof the metal plate includes placing the metal plate such that theenlarged diameter portion of the cut-out portion becomes a bottomsurface side of the annular concave portion.
 12. The method ofmanufacturing a recording tape cartridge of claim 9, wherein positioningof the metal plate includes fixing the metal plate by an annularmagnetic body disposed at a bottom surface of the annular concaveportion of the fixed side mold plate.